This invention relates to the scrambling of multi-value digital (non-binary) signals and the generation of multi-value (non-binary) digital signals consisting of sequences of multi-value (non-binary) digital elements such as n-value pseudo-noise sequences. Multi-value signals, also referred to as x-value signals, can assume one of x states, wherein x is greater than or equal to three.
Its potential application is in telecommunication systems, control systems and other applications. Specific examples of utility where the invention can be used include spread-spectrum technologies, signal scrambling, CDMA, line-coding and scrambling application in video and other signal distribution.
Digital scramblers are used to change the appearance of a digital signal in such a way that during transmission the signal is different from the original signal. The original signal can be recovered from the scrambled signal at the receiving end by a descrambler. Most commonly in today's telecommunications, the scramblers relate to binary signals.
Scrambling of a binary signal can be achieved by combining the binary signal to be scrambled with a second known binary signal through a digital circuit that has the characteristics of a reversible function. The inventor has recognized that the reversible function has the property that its two inputs generate an output. When applying this output as the input to another, but similar, circuit with as the other input a signal similar to the known input of the first digital circuit, the output of the second circuit is identical to the to be scrambled data signal input of the first circuit. This other circuit is a descrambler.
There are two known binary functions that can perform this reversible function: the Exclusive Or (XOR) and the Equal function. The XOR function is also known as the modulo-2 adding function.
Telecommunication markets such as wireless communications and internet communications demonstrate an ongoing increase in demand for higher information transmission rates. This demand in increased information transmission rates in wireless communications is addressed by increasing bandwidth of communication channels, by compression of the information and by moving into much higher radio spectra (such as Ultra Wide Band in the 5 GHz area). Eventually, new technology has to be applied to obtain better performance from existing bandwidth, starting with highly congested spectrum areas. Current transmission technology predominantly uses digital binary signals. One possible technology to provide better bandwidth usage is the application of multi-value digital signals. Scrambling, descrambling and signal sequence generation is an important element of signal processing technology, especially in wireless communications. However, currently very little technology exists in prior art that can perform multi-value digital scrambling, descrambling and sequence generation. Most of prior art in scrambling, descrambling and sequence generation only performs binary functions, as previously discussed.
Consequently, new and improved methods and apparatus to perform scrambling, descrambling and sequence generation on non-binary, multi-value digital signals are required.
The existence of multi-value reversible logic functions has been previously mentioned. However, no mention has been found of multi-value reversible logic in scrambling/descrambling applications, nor in the generation of multi-value signal sequences.